1. Field of the Invention
The present invention is related to an image formation apparatus with a sheet delivery structure which facilitates a smooth transfer of a toner image.
2. Description of the Related Art
An image formation apparatus such as a copier, a facsimile apparatus or a printer typically has a transfer structure for transferring a toner image formed on an image carrier to a sheet. The transfer structure has a photosensitive drum which is used as the image carrier, a transfer roller which forms a nip portion in cooperation with the photosensitive drum, and a guide element which guides the sheet nearby the peripheral surface of the photosensitive drum.
The guide element includes a main guide configured to define a delivery path through which the sheet passes, and a sub-guide attached to the main guide. The main guide has a tip portion near the peripheral surface of the photosensitive drum. The sub-guide which protrudes from the tip portion of the main guide toward the nip portion partially occupies a space from the tip portion of the main guide to the nip portion, so that the sheet is stably supported by the sub-guide. Thus, failures in toner image transfer because of trailing end flapping of a sheet become less likely.
The aforementioned sub-guide is formed of a synthetic resin film. In addition, a thickness of the sub-guide is determined for appropriate elastic characteristics, which work for better adhesion of the sheet to the peripheral surface of the photosensitive drum.
Friction between the sub-guide made of synthetic resin and a sheet causes electrostatic charge of the sub-guide. The electrostatic charge of the sub-guide causes toner scattering from the photosensitive drum. Contamination of the sub-guide resulting from the toner scattering eventually causes stains on the sheet (stains on a blank surface opposite to a transfer surface onto which the toner image is transferred).
An increase in distance between the sub-guide and the photosensitive drum in order to avoid the stains on the blank surface results in insufficient support for a sheet moving toward the nip portion. As a result, failures in the transfer may be caused by the sheet flapping.